By Philip Pullella

VIENNA, Sept 9 (Reuters) - Pope Benedict on Sunday called on Catholics to keep the Sabbath a day set aside for reflection on their faith and the fate of the world and not surrender it to "the mad rush of the modern world".

The Pontiff made his call on the last day of a trip to Austria during a Mass in Vienna's majestic St. Stephen's Cathedral whose colourfully patterned tiled mosaic roof and 136-metre high (445 feet) tower are the city's main landmark.

The Pope said Western societies had transformed Sundays into days where leisure activities had eclipsed the traditional Catholic meaning of the day -- to devout time to God.

"Give the soul its Sunday, give Sunday its soul," he said, quoting a phrase coined by a German bishop in the 20th century.

Austria, like many other Western European countries, has seen declining Church attendance on Sunday, just one sign of what Benedict sees as a rapid decline in religious sentiment that he would like to see turned around.

The issue of Sunday also has economic ramifications in predominantly Catholic Austria.

Most shops are not allowed to open and there has been some pressure from business groups and shop operators to get the right to open on Sunday, a move Catholic groups oppose.

Calling Sunday the Church's "weekly feast of creation," the Pope said the day should also be a weekly reminder of the dangers to the planet.

"At a time when creation seems to be endangered in so many ways through human activity, we should consciously turn our attention to this dimension of Sunday too," he said, speaking in German.

Last Sunday in central Italy, Benedict led the Catholic Church's first 'eco-friendly' youth rally and told up to half a million people that world leaders must make courageous decisions to save the planet "before it is too late".

Under Benedict and his predecessor John Paul, the Vatican has become progressively "green". It has installed photovoltaic cells to produce electricity and hosted a scientific conference to discuss the ramifications of global warming and climate change, widely blamed on human use of fossil fuels.

In July, Benedict said the human race must listen to "the voice of the Earth" or risk destroying its very existence.

The Pope, on his seventh trip outside Italy, since his election in 2005, was due to visit a monastery and address Catholic volunteer groups before returning to Rome on Sunday night.

(additional reporting by Karin Strohecker and Christian Gutlederer)

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